go down to the fishing dock, down town by the rail road tracks before you get to the square. look for the terra cotta colored building on the right. you'll see the boats anchored in the bay. I have the best luck with the boat 'Perla'. cost around $150-$200 US per 5 hours for the boat.
No need to go thru resort tout, just go down and talk directly to the captain. go at noon so you can see the day's catch.